Friction welding



May 26, 1964 M. B. HOLLANDER ETAL FRICTION WELDING FlG.I

O PRESSURE IN |000 lbs/ Sq.n.

\ 1 y r u l0 2O 30 40 50 60 Original Filed March 8, 1961 FIG.2

ZZ (2o) @ff RELATIVE SURFACE SPEED IN FEET/SECOND FIGA POWE R KILOWATTSTOROUE lnchlbs. m oa wELo UME o s'o so m sEcoNos j FIGJ PRESSURE |000lbs/Sq in. I ra 4 m a:

o fo z'o 3`o o sro sb 7o sb 4new TIME 1N sEcoNns iNvENTOrs MLTON BERNARDHOLLANDER MICHAEL' FRANCIS GAMFS-CAMPINSv United States Patent C3,134,169 FRICTION WELDING Milton Bernard Hollander, Stamford, andMichael Francis Camps-Campins, Norwalk, Conn., assignors to AmericanMachine & Foundry Company, a corporation of New Jersey Continuation ofapplication Ser. No. 94,311, Mar. 8,

1961. This application Apr. 24, 1963, Ser. No. 275,311 Claims. (Cl.29470.3)

This invention relates in general to welding processes, and, moreparticularly, to friction or spin welding.

This application is a continuation of our copending application SerialNo. 94,311, filed March 8, 1961, and now abandonded.

An object of this invention is to provide a stronger friction weld.

Another object of this invention is to accomplish a superior frictionweld which produces a smaller upset which is easier to clear away andconserves weld material.

Still another object of this invention is to provide a weld, which, byits nature of formation and final characteristics, can serve to join andseal thin walled sections which cannot he accomplished by a conventionalfriction welding cycle.

A further object of this invention is to accomplish a superior frictionweld using a heretofore unknown range of welding pressures and relativesurface speeds.

Additional objects, advantages and features of invention reside in theparticular steps of this process of welding and their application aswill be described in the specication and accompanying drawing in which:

FIG. l is a graph of pressures and relative surface speeds showing theareas within which friction welding according to this invention may bebest accomplished.

FIG. 2 is an end view of a workpiece to be friction Welded;

FIG. 3 is a side view of two workpieces about to be friction welded;

FIG. 4 is a side view of the two workpieces being rotated relative tocach other and brought together at the start of a friction weldingcycle;

FIG. 5 is a side vicw of the two workpieces after the completion of thefriction welding cycle of this invention;

FIGS. 6 and 6A are longitudinal sections through frag ments of twofriction welded workpieces showing the weld area and the upset as itgenerally appears when workpieces are conventionally friction welded;

FIG. 7 is a longitudinal section through a fragment of two frictionwelded workpieces showing the weld area and the upset as it appears whenthe workpieces are friction welded according to this invention;

FIG. 8 is a graph of the power requirement plotted against welding timein seconds for a conventional friction welding cycle and for the`process of this invention;

FIG. 9 is a graph of the required torque plotted against welding timefor a conventional friction welding cycle and for this invention; and

FIG. l() is a graph of the pressure which is applied to twoworkpiecesplotted against the weld time in seconds for a conventionalfriction welding cycle and for this invention.

Referring to the drawing in detail, FIG. 2 shows an end view of aworkpiece 20 which contains a longitudinal channel 2l. In one group ofsamples which were tested, the outside diameter of the workpiece 20 was1% inches while the diameter of the channel 2l was 7/s inch.

As shown in FIG. 3, a workpiece Ztl and an identical workpiece 22 are tobe friction welded. At least one of the workpieces is rapidly rotatedrelative to the other.

As shown in FIG. 4, one of the workpieces is advanced towards the otherduring this relativerotation. Fric- 3,134,169 Patented May 26, 1964tional heat is evolved until, at a desired moment, the relative rotationis rapidly stopped and the pieces 20 and 22 are forced together formingthe upset 23.. This is the basic manner in which all friction welding isaccomplished.

If the two workpieces 20 and 22 were of a steel such as 1045 or 4140steel, the conventional and heretofore only known range of pressures andrelative surface speeds within which friction welding couldsubstantially be accomplished is indicated generally on FIG. l Withinthe area indicated by the numeral 24. The numeral 50 indicates the areawithin which alloy steels and tool steels are conventionally frictionwelded while the numeral 51 indicates the area within which bronzes,aluminums and coppers are conventionally friction welded.. These areas24, 50 and 51, within which conventional friction welding isaccomplished, use relatively high pressures to force the workpiecestogether during the period of their relative rotation. At the same time,the relative surface speed in the area of contact between the workpiecesis comparatively low. From an evaluation of many samples welded withconventional friction welding techniques, it may be inferred that thesetechniques give rise to a pressure forging or a solid phase welding inthat it is mainly the large pressure applied during rotation whichcauses the material to become plastic and flow.

Referring now to FIGS. 8 through l0, if two workpieces 20 and 22 ofsteel are friction welded using conventional techniques and theworkpieces are of the dimensions stated, the dotted line 2S in FIG. 10iindicates the manner in which pressure is applied during a conventionalwelding cycle. The entire conventional welding cycle occupies acomparatively short period of time usually of the order of about 5 to 2Oseconds. While a relatively high pressure is applied during the relativerotation of the workpieces, a considerably higher upset pressure may beapplied after the relative rotation ceases. This high pressure, which isapplied after rotation stops, is indicated on FIG. l0. As shown in FIG.8, the power requirement during a conventional weld cycle is indicatedby the dotted line 26. This power requirement falls oft" only slightlyfrom its peak value during the weld cycle. In a like manner, the torquebetween the workpieces remains relatively high during the entireconventional welding cycle as indicated by the dotted line 27 in FIG. 9.

When using the welding technique of a conventional friction weldingcycle to accomplish even an adequate weld of steel workpieces, certainupset pressures must be maintained. When such a weld is accomplished asshown in FIGS. 6 and 6A, the upset 2S and 2S from a conventional weldingcycle has a particular characteristic appearance. It curves upwards andoutwards from the weld arca and has the characteristic circumferentialserrations 29 formed on both its inward facing outer surfaces. Thesurface 29 resemblies the outer surface of a Type 2 chip from metalcutting. In metal cutting, such a surface is formed by shearing.

Referring again to FIG. 1,!'the general range of pressures and relativesurface speeds embraced by this irivenf tion are indicatedgenerally lbythe area designated by4 numeral 3i). As may be seen, 'the surface speedsare conA siderably greater thian'those used in conventional friction'welding techniques and the pressures involved during frictio'nalheating are considerably lower.

Referring again to FIGS. 8, 9 and 10, the welding cycle of thisinvention often takes a longer time than the conventional welding cycleand, for the workpieces 20 and 22, may be upwards of seconds. l

As shown in FIG. l0, the pressure is graduallyv increased during theperiod of relative rotation ofthe workpieces up to a given point whereonit is held constant. As indicated in FIG. l0, the solid line 31 showsthe: typical pressures applied to the workpieces'plotted against theweld 3 time in seconds. The segment 32 of line 3l indicates the gradualincrease of pressure during the first phase of the relative rotation ofthe workpieces. The segment 33 of line 31 indicates the period ofconstant pressure during the welding cycle. This portion may varyconsiderably depending on the size of the objects being weldedl and thematerials involved. Segment 34 of line 31 starts at the completion ofthe relative rotation of the workpieces and' indicates the comparativelyhigher upset pressures applied to the workpieces after their relativerotation is stopped. In the practice of this invention, these upsetpressures are rarely as high as those required in a conventionalfriction welding cycle. Segment 34 of line 31 indicates the time ofapplication of the upset pressure when welding 1020 steel. 34' and 34"indicate the later time of applying the upset pressure to 1045 and 4140steels.

Referring now to FIG. 9, the torque applied during the weld cycle ofthis invention for steels is plotted against the welding time in secondsand indicated by the solid line 35. As indicated by the segment 36 ofline 35, the torque between the workpieces increases to a peak duringthe first fifteen seconds or so of this welding cycle. At this point, asindicated by segment 37 of line 35, the torque between the pieceslluctuates rapidly. As indicated by thc segment 38 of line 35, thetorque between the workpieces continues to drop off and approaches aconstant value during the remainder of the welding cycle until therelative rotation between the workpieces is rapidly stopped as indicatedby the segment 39 of line 35. The time at which the relative rotation ofthe workpieces is stopped depends on the steel or material being welded.Line 39 indicates the general stopping time for 1020 steel, 39 indicatesthe general stopping time for 1045 steel and 39 indicates a stoppingtime for 4140 steel.

As shown in FIG. 8, the power requirement for this welding cycle isplotted against the weld time in seconds and indicated by a line 40. Asindicated by the segment 41 of the line 40, the power requirementreaches a peak at about the same time as the torque between theworkpieces reaches a peak as indicated by the erratic segment 42 of theline 40. As indicated by the segment 43 of the line 40, the powerrequirement gradually falls off approaching a constant value during theremainder of the welding cycle of this invention until the relativerotation of the workpieces is rapidly stopped. The power requirement isbasically identical to the torque requirement except for frictionallosses in the welding apparatus. The lines 55, 55 and 55" indicatestopping times for different steels.

The friction welding cycle of this invention gives rise to an entirelynew phenomena in that the highensurface speeds and the lower pressuresenable the metal of the workpieces 20 and 22 in the weld area to becometluid. This thin layer of fluid within the weld area may act las ahydrodynamic bearing during the latter portion of this welding cycle.

As shown in FIGS. 8, 9 and l0, the torque starts to fall off from thepeak of the segment 36 of the line 35 as the hydrodynamic bearingerratically forms and interthe theory that the molten lm of metalalternatively isl formed and then fails so that there are intermittentseizures within the weld area until sufficient heat is generated toprovide a continuous molten film whereon the torque smoothly falls offas indicated by the segment. 38 of the line 35 and the segment 43 of theline 40.

As shown in FIG. l0, after the relative rotation of the workpieces 20and 22 is stopped, an upset pressure, indicated by the segments 34. 34'and 34" of the line 3l. is applied. This causes molten and plastic metalto llow and form the upset 45 as shown in FIG. 7. This upset 45 ischaracterized in that it is considerably smaller than the upset 28 ofthe conventional friction welding process. Furthermore, the upset 45 ischaracterized in that it has smooth outer facing surfaces 46 which donot have the relatively large circumferential.scrrations 29 of theconventional upsets 28 and 28'. t

Referring again to FIG. l, the average relative surface speeds withinthe weld area 30 which are within the contemplation of this inventionfor the friction welding of steels vary from about 15 feet per second to70 feet per second. In order to weld at all, the pressures duringrotation must be at least 1000 pounds per square inch for steel.However, should these pressures increase much over 10,000 pounds persquare inch, the metal lm formed during the heating cycle breaks downand localized seizure takes place resulting in accompanying chatter andnonuniformity of the weld. Thus the upper limits of the pressures whichmay be used within the contemplation of this invention are those whichtend to break down the thin molten film with too great a load capacity.

As is further shown in FIG. l, the area 30, within which the weldingcycle of this invention may be carried out for steels, is considerablyremoved from the area 24 within which a conventional welding cycle forsteels is carried out. Between these two areas there is an area in whichfriction welding may not be carried out without excessive power orltorque requirements, overly large upset, seizure between theworkpieces, and resulting uneven and irregular friction welds.

The expression average relative surface speed as employed herein and inthe appended claims describes the velocity at a point on theface oftheworkpiece which is moving at an average velocity relative to theinside and outside radius, and is dened by the equation:

V=average relative surface speed, feet per second N :the angular speedof one piece sliding relative to the other, revolutions per minute0.D.=outside diameter, in.

vI.D.=inside diameter, in.

Essentially, the equation averages the velocity across the proflle ofthe workpiece. If the workpiece is a solid bar, the average relativesurface speed is the velocity at 2/2. the radius of the bar.

What is claimed is:

l. The process of friction welding steel workpieces comprising the stepsof establishing a relative rotation between workpieces with an averagerelative surface speed between l5 and 70 feet per second, forcing saidworkpieces together with a pressure from 1000 to 10,000 pounds persquare inch in the area of contact between the workpieces, rapidlystopping the relative rotation of the workpieces, and thereafterapplying a higher pressure forcing the workpieces together and moltenmetal from the area of Contact. 4

2. The process according to claim l in which the higher pressure in theweld area is maintained until the meal cools and hardens.

3. The process according to claim l in which the period of relativerotation of the workpieces lasts more than 30 seconds.

4. The process according to claim l in which both the entire step ofrapidly stopping the relative rotation ot' the workpieces and thestarting of the step of applying a higher pressure forcing theworkpieces together take place in less than 2 seconds.

5. The process of friction welding steel workpieces comprising the stepsof rotating workpieces relative to each other with an average relativesurface speed between 15 and 70 feet per second, forcing the relativelyrotating workpieces together with a pressure from 1000 to 10,000 poundsper square inch in the area of contact between the relatively rotatingworkpieces until a film of molten metal forms in the area of Contactbetween the relatively rotating workpieces, rapidly stopping therelative rotation of the workpieces, and continuing forcing theworkpieces together to upset metal from the area of contact between saidworkpieces.

UNITED STATES PATENTS Nelson Apr. 12, 1927 Lytle et al July 25, 1944Crowe Nov. 3, 1953 Jendrisak et a1 Oct. 18, 1960 FOREIGN PATENTS GreatBritain Oct. 24, 1945

1. THE PROCESS OF FRICTION WELDING STEEL WORKPIECES COMPRISING THE STEPSOF ESTABLISHING A RELATIVE ROTATION BETWEEN WORKPIECES WITH AN AVERAGERELATIVE SURFACE SPEED BETWEEN 15 AND 70 FEET PER SECOND, FORCING SAIDWORKPIECES TOGETHER WITH A PRESSURE FROM 1000 TO 10,000 POUNDS PERSQUARE INCH IN THE AREA OF CONTACT BETWEEN THE WORKPIECES, RAPIDLYSTOPPING THE RELATIVE ROTATION OF THE WORKPIECES, AND THEREAFTERAPPLYING A HIGHER PRESSURE FORCING THE WORKPIECES TOGETHER AND MOLTENMETAL FROM THE AREA OF CONTACT.